The discovery of ultraconfined polaritons with extreme anisotropy in a number of van der Waals (vdW) materials has unlocked new prospects for nanophotonic and optoelectronic applications. However, the range of suitable materials for specific applications remains limited. Here we introduce tellurite molybdenum quaternary oxides—which possess non-centrosymmetric crystal structures and extraordinary nonlinear optical properties—as a highly promising vdW family of materials for tunable low-loss anisotropic polaritonics. By employing chemical flux growth and exfoliation techniques, we successfully fabricate high-quality vdW layers of various compounds, including MgTeMoO₆, ZnTeMoO₆, MnTeMoO₆ and CdTeMoO₆. We show that these quaternary vdW oxides possess two distinct types of in-plane anisotropic polaritons: slab-confined and edge-confined modes. By leveraging metal cation substitutions, we establish a systematic strategy to finely tune the in-plane polariton propagation, resulting in the selective emergence of circular, elliptical or hyperbolic polariton dispersion, accompanied by ultraslow group velocities (0.0003c) and long lifetimes (5 ps). Moreover, Reststrahlen bands of these quaternary oxides naturally overlap that of α-MoO₃, providing opportunities for integration. As an example, we demonstrate that combining α-MoO₃ (an in-plane hyperbolic material) with CdTeMoO₆ (an in-plane isotropic material) in a heterostructure facilitates collimated, diffractionless polariton propagation. Quaternary oxides expand the family of anisotropic vdW polaritons considerably, and with it, the range of nanophotonics applications that can be envisioned.

在许多范德华（vdW）材料中发现具有极端各向异性的超约束极化子，为纳米光子和光电应用开辟了新的前景。然而，适合特定应用的材料范围仍然有限。在这里，我们介绍亚碲酸盐钼四元氧化物，它具有非中心对称晶体结构和非凡的非线性光学特性，是一种非常有前途的 vdW 系列材料，可用于可调谐低损耗各向异性极化子。通过采用化学助熔剂生长和剥离技术，我们成功地制造了各种化合物的高质量vdW层，包括MgTeMoO ₆、ZnTeMoO ₆、MnTeMoO ₆和CdTeMoO ₆。我们证明这些四元 vdW 氧化物具有两种不同类型的面内各向异性极化激元：板限制模式和边缘限制模式。通过利用金属阳离子取代，我们建立了一种系统策略来微调面内极化子传播，从而选择性地出现圆形、椭圆形或双曲极化子色散，并伴有超慢群速度（0.0003 c ）和长寿命（5 ps） ）。此外，这些四元氧化物的 Reststrahlen 带自然地与 α-MoO ₃的带重叠，提供了集成的机会。作为一个例子，我们证明了将 α-MoO ₃（一种面内双曲材料）与 CdTeMoO ₆（一种面内各向同性材料）组合在异质结构中有助于准直、无衍射极化子传播。四元氧化物极大地扩展了各向异性 vdW 极化激元家族，并由此扩展了可以预见的纳米光子学应用范围。